A variety of diseases exist that require regular treatment by injection of a medicament. Such injections can be performed by using injection devices. Various injection pumps for delivering bolus injections are known in the art. Generally such devices are operated by the patient's themselves, although they may also be operated by medical personnel.
To use an injection pump, it is first supported on a suitable injection site on a patient's skin and, once installed, injection is initiated by the user. Typically, the initiation is effected by the user operating an electrical switch, which causes a controller to operate the device. Operation includes firstly injecting a needle into the user and then causing the injection of medicament into the user's tissue. Biological medicaments are being increasingly developed which comprise higher viscosity injectable liquids and which are to be administered in larger volumes than long-known liquid medicaments. Large volume devices (“LVDs”) for administering such biological medicaments may comprise a pre-filled disposable drug delivery device or, alternatively, a disposable drug delivery device into which a patient or medical personnel must insert a drug cartridge prior to use.
There are typically a number of steps that need to be performed for use of injection devices by the user before medicament injection can begin. Whilst handling the device in the pre-injection phase of operation it is possible that the user may accidentally initiate the injection and then medicament delivery. This can occur either when the patch pump is not installed on the user at all or when the device is only partly installed and is not secured at the correct location on the user. Such errors are at best inconvenient and at worst can present safety issues.